In a wireless communication system, the capacity and coverage are two important performance indicators. In order to increase the capacity, the common frequency mode is generally used for networking. However, networking by the common frequency mode increases inter-cell interference, thus resulting in the degrading in the coverage performance.
For example, in a Long Term Evolution (LTE) system, the Orthogonal Frequency Division Multiple Access (OFDMA) technique is used in downlink, and the Single Carrier-Frequency Division Multiple Access (SC-FDMA) technique is used in uplink. However, since the common frequency mode is generally used in networking, the Inter-Cell Interference (ICI) increases apparently. In order to reduce the ICI, the LTE adopts some anti-interference techniques, e.g., the downlink Inter-Cell Interference Cancellation (ICIC). The downlink ICIC technique realizes the function of downlink interference advance warning on the basis of a method for Relative Narrowband TX Power (RNTP) limiting of an evolved Node B (eNodeB), and enhances the coverage performance of the Physical Downlink Shared Channel (PDSCH). The uplink adopts an ICIC technique based on the High Interference Indication/Overload Indication (HII/OI) and enhances the coverage performance of the Physical Uplink Shared Channel (PUSCH).
In addition, the Channel Coding technique and the Multiple Input Multiple Output (MIMO) technique have made important contributions to the improvement of the link transmission performance, so that the data can resist various types of fading in the channel. The MIMO technique, especially the Coordinated Multiple Point (CoMP) technique which is developed on the basis of the MIMO technique, can also improve the coverage performance and capacity performance of the LTE system by means of the Spatial Diversity, Spatial Multiplex and beam-forming techniques. However, the MIMO technique and CoMP technique rely heavily on the measurement and feedback of the channel state information. The User Equipment (UE) having a very low signal-to-noise ratio is still a bottleneck for the measurement and feedback of the wireless channel in the wireless system during a period of time at present and in the future: on the one hand, the more complete and accurate the feedback is, the larger the feedback amount is, which is a challenge to the capacity and coverage distance; on the other hand, it is very difficult to guarantee the feedback delay and the accuracy for a fast fading channel. Therefore, for a UE of which the coverage is limited, it is very difficult for the closed-loop MIMO technique and CoMP technique to acquire the required gain, instead, the simple and practical open-loop MIMO technique is often adopted. The open-loop MIMO technique is generally combined with resource frequency hopping, because the resource frequency hopping is a quasi-open-loop resource allocation technique, the subsequent resource allocation is determined by means of a frequency hopping manner and initial resource allocation, thereby saving resource allocation cost and feedback cost.
There are multiple techniques which can improve the transmission performance of the system in the LTE system, especially the coverage performance. However, it is found from experimental network tests and simulations that the PUSCH with a medium data rate, the PDSCH with a high data rate and Voice over IP (VoIP) services are still channels of which the coverage performance is limited in the channels in the LTE system. The main reason lies in that the limited UE transmission power results in the PUSCH with the medium data rate and the VoIP being limited, and the ICI between base stations results in the PDSCH with the high data rate being limited. This proposes the requirement for the improvement of the LTE system coverage performance, and for this purpose, the Transmission Time Interval (TTI) Bundling technique is introduced to the LTE system. The TTI Bundling technique forms various redundancy versions for the entire data packet by means of Channel Coding, wherein various redundancy versions are respectively transmitted in multiple successive TTIs, and the transmission in multiple non-successive TTIs is also under evaluation. The TTI Bundling technique acquires the coding gain and the diversity gain by occupying more transmission resources so as to acquire higher receiving power and link signal-to-noise ratio, thereby improving the coverage capability of the LTE system. In exchange for the coverage performance, the TTI Bundling technique reduces the spectrum efficiency, and is mainly used in a UE having a very low signal-to-noise ratio. Generally, for the UE having a very low signal-to-noise ratio, the coverage performance thereof may also be improved by means of the diversity technique, for example, the frequency diversity technique. In the existing LTE standard technologies, the TTI Bundling and the frequency diversity may be used at the same time. However, when the existing TTI Bundling technique and the existing frequency diversity technique are combined, the acquisition of the frequency diversity gain and the increase of the control cost are limited to some extent, this is because the existing frequency diversity technique is not designed specially for the TTI Bundling technique.
For example, as shown in FIG. 1, the first transmission of the first VoIP packet from the UE is performed at the Transmission Time Intervals 4 to 7 of the Physical Uplink Shared Channel (PUSCH), with the four successive TTIs from 4 to 7 being referred to as a TTI Bundling of which the TTI Bundling Size is 4. The control information (e.g., the resource position etc.) of the TTI Bundling is indicated by the Physical Downlink Control Channel (PDCCH) in the TTI 0 corresponding to the first TTI (TTI 4) in the TTI Bundling. After receiving the TTI Bundling, a receiving end (e.g., an eNodeB) indicates the Acknowledge/Non-Acknowledge (ACK/NACK) response information of the Hybrid Automatic Repeat Request (HARQ) entity on a downlink Physical HARQ Indication Channel (PHICH) at the Transmission Time Interval 12. If the corresponding response is a negative response NACK, the second transmission of the first VoIP packet (i.e. the first retransmission of the TTI Bundling) will be performed on the Physical Uplink Shared Channel (PUSCH) at the Transmission Time Intervals 21 to 24, and the corresponding Acknowledge/Non-Acknowledge (ACK/NACK) response of the Hybrid Automatic Repeat Request (HARQ) entity is transmitted on the downlink PHICH at the Transmission Time Interval 28; and so on, until the corresponding response is an Acknowledge (ACK) response, or the maximum number of times of transmission attempt (e.g., 4 times) is reached, the transmission of the first VoIP packet ends. Similarly, the manner of the transmission of the nth VoIP packet is the same as that of the transmission of the first VoIP packet. It can be seen from the transmission as shown in FIG. 1 that when the resource blocks allocated to the TTI Bundling are centralized resource blocks, that is, the physical positions of the resource blocks in two Slots within one TTI are the same, the physical positions of the resource blocks of multiple TTIs in one TTI Bundling are exactly the same, and in order to save control cost under the Semi-Persistent Scheduling (SPS), the physical positions of the resource blocks in successive TTI Bundlings are exactly the same, which will seriously limit the acquisition of the frequency diversity gain. The physical positions of the resource blocks in the TTI Bundling may be changed by adding the transmission of the PDCCH, but the control cost will be apparently increased, and the physical positions of the resource blocks of multiple TTIs in one TTI Bundling are exactly the same. When the resource blocks assigned to the TTI Bundling are centralized resource blocks, that is, the physical positions of the resource blocks in two Slots within one TTI are different, two Slots within one TTI cannot adopt joint channel estimation, the accuracy of the channel estimation will be degraded and the system performance will also be degraded.
An enhanced TTI Bundling technique is proposed on the basis of the TTI Bundling technique of the LTE R8, for example, as shown in FIG. 2. The interval between two TTI Bundlings is 4 TTIs, the first transmission and retransmission may use one HARQ process or multiple (e.g., two) HARQ processes; similarly, the interval between two TTI Bundlings is 8 TTIs, the first transmission and retransmission may use one HARQ process or multiple (e.g., two) HARQ processes. However, the enhancing theories thereof are to increase the maximum number of TTIs occupied by the first transmission and retransmission of a VoIP packet altogether from 12 or 16 to 20, thereby improving the accumulated transmission power or adding the redundancy versions of the HARQ, but is still the same as the mechanism of the LTE R8 in the aspect of the resource allocation of the TTI Bundling and seriously limit the acquisition of the frequency diversity gain.
In summary, as regards the Transmission Time Interval Bundling technique in related technologies, the lower frequency diversity gain results in the problem of the smaller data transmission coverage area, and no effective solution has been proposed at present.